Bump @anthropic-ai/sdk from 0.80.0 to 0.81.0 in /chat-lib (#4915)

Bumps [@anthropic-ai/sdk](https://github.com/anthropics/anthropic-sdk-typescript) from 0.80.0 to 0.81.0.
- [Release notes](https://github.com/anthropics/anthropic-sdk-typescript/releases)
- [Changelog](https://github.com/anthropics/anthropic-sdk-typescript/blob/main/CHANGELOG.md)
- [Commits](https://github.com/anthropics/anthropic-sdk-typescript/compare/sdk-v0.80.0...sdk-v0.81.0)

---
updated-dependencies:
- dependency-name: "@anthropic-ai/sdk"
  dependency-version: 0.81.0
  dependency-type: direct:development
...

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